Ash, Goh, and Chloe in Alola
Following Lillie's family reunion at the Crown Tundra, Ash, Goh, and Chloe have joined the Aether family on a journey back to Alola, with Chloe being excited to visit the region for the first time. They arrive on Melemele Island, where Mallow's family has organized a big feast to celebrate Mohn's homecoming. Lillie is overjoyed to meet her classmates again, while Hobbes, Faba, and Wicke are shedding tears for seeing Mohn return home safe and sound. While everyone and their Pokémon feast, Chloe's Eevee meets Lana's Eevee, Sandy, and they quickly befriend each other. Chloe goes over to Lana to talk about Sandy, telling her how she and her Eevee have met many of Eevee's evolutions, but are still unsure which of them she should choose. Lana tells Chloe that there's also one more possible path to consider: not evolving Eevee at all, similar to how Ash's Pikachu has chosen not to evolve. Meanwhile, Goh notices the absence of Kiawe, which is explained to be due to him having gone off to train at Wela Volcano as soon as he had heard that Ash was coming back to Alola. Ash's classmates also reveal that they watched his World Coronation Series entrance battle against Raihan, since he's the Alola League Champion. While the conversation continues, Gladion wanders into the nearby woods to do some training of his own.
Once the feast is over, Ash, Goh, and Chloe gather at Professor Kukui's house, where they learn that there's going to be a Battle Royal at the Battle Royal Dome the next day. While Kukui wants to keep Ash's opponents a secret, he does reveal that he is one of them. Ash asks if Kukui if he'll be appearing as the Masked Royal, but while Kukui briefly agrees to put on his costume, he makes it clear that he'll be facing Ash as himself, since Ash is the Alola League Champion and therefore the star of the show. Eager for what's to come, Ash invites his Pokémon to do some training.
The next day, the attention of the entire Alola region is focused on the Battle Royal Dome as the Battle Royal to celebrate the Alola League Champion's homecoming is about to begin. Working as the MCs, Faba and Wicke introduce the competitors. To no surprise, the first competitor is Ash, accompanied by Pikachu. The next participant is Professor Kukui, the founder of the Alola League, joined by his partner, Incineroar. The third team is the island kahuna hopeful Kiawe and his Marowak. Finally, last but not least, the final participating team is the Alola League runner-up Gladion and Lillie the Nihilego.
With the ring of a bell, the Battle Royal is underway. Ash and Pikachu immediately find themselves under a relentless assault as all of his opponents target Pikachu with their attacks, an example of how in a Battle Royal, anyone can target anybody. A second volley of attacks is launched at Pikachu in the form of Lillie's Meteor Beam, Marowak's Flare Blitz, and Incineroar's Darkest Lariat, but Pikachu manages to evade them all by using Quick Attack, utilizing his great Speed to his advantage. A third wave of attacks is likewise evaded, with Pikachu even managing to knock Incineroar off-balance with Iron Tail. Kukui notes that Ash has gotten stronger, but Kiawe and Gladion assure that so have they. Pikachu counters the next barrage with a Thunderbolt, following up with an Electroweb. While Incineroar briefly gets trapped in it due to Blast Burn's recharging time, it quickly escapes from it with Throat Chop, meeting Pikachu's flurry of Iron Tails with its own rapid-fire attacks, until they're forced apart by Lillie's Meteor Beam.
For the first time in the match, Kiawe targets someone else than Ash, having Marowak attack Lillie with Shadow Bone while swearing to be the one to defeat Ash. Gladion responds with the same vow and has Lillie attack Marowak with Venoshock. Marowak avoids the attack and strikes back with Iron Head, taking Gladion's Ultra Beast out of the fight. Despite this loss, though, Mohn and Lusamine are still proud of their son as they watch him from the audience. Kiawe then turns his attention back to Ash and declares that he'll be going all out, starting to perform his Z-Move poses with Marowak. As Marowak's Inferno Overdrive goes off, Ash has Pikachu use Thunderbolt to propel himself upwards, successfully evading the Z-Move. At that moment, Kukui and Incineroar reenter the fray with another Darkest Lariat, which hits both Pikachu and Marowak, taking the latter out of the match.
With Ash and Kukui being the only competitors left, they can't help but be reminded of the time when they faced each other in the Alola League exhibition match. Ash is snapped out of his reminiscing when he hears the entire dome chanting in support for their Champion. He is taken aback at first, but soon enough, he begins to embrace the cheering and support the entire region is giving him with a smile. Goh and Chloe are also initially surprised when they come to fully realize that Ash is a local celebrity. Kiawe and Gladion tell Ash to win the Masters Eight Tournament as a representative of Alola and encourage him to use his full power. Happily accepting this request, Ash tosses his hat to Pikachu as they begin to perform their own Z-Move. Professor Kukui responds in kind, and a brilliant flash illuminates the Battle Royal Dome as Pikachu's 10,000,000 Volt Thunderbolt and Incineroar's Malicious Moonsault clash in a powerful display of signature Z-Moves.
Later, Professor Kukui meets Ash at the beach near his house and asks what he's thinking about. Looking at the sunset, Ash says that he's happy he came to Alola. Suddenly, they're greeted by Tapu Koko, who performs a dance that Kukui interprets as it praying for Ash's victory. Ash promises to do his best in the Masters Eight Tournament and watches as Tapu Koko flies away, smiling at the knowledge that the entire Alola region is supporting him as he heads towards his greatest challenge yet.